1. Field
The present disclosure relates to an embroidery frame holding workpiece cloth for execution of an embroidering function and a sewing machine to which the embroidery frame is attachable.
2. Description of the Related Art
Conventional sewing machines with an embroidering function have provided with an embroidery frame detachably attached to a sewing machine body so that workpiece cloth to be sewn is retained. The embroidery frame conventionally includes an inner frame, an outer frame and an adjusting screw tightened or loosened so that the inner and outer frames are coupled to and decoupled from each other. Recently, however, the sewing machine of the above-described type is provided with a lower frame, an upper frame and a clamping mechanism pressing the upper frame against the lower frame and retaining both frames in the pressed state.
As a first conventional example, JP-A-H08-238391 discloses a clamp type holding frame for cloth to be sewn. The disclosed frame comprises a base frame (a lower frame), a pressing frame (an upper frame), a pair of right and left clamping mechanisms pressing and fixing the pressing frame against and to the base frame so as to be released from each other, a linking mechanism linking the pressing frame to the base frame 1 so that the pressing frame is vertically swingable and a pair of air cylinders driving the pressing frame via the linking mechanism. As the result of the above-described construction, when the air cylinders are driven, the pressing frame is displaced between a pressing/fixing position and a releasing position. See pages 3 and 4 with reference to FIG. 4 in the first example.
In the aforementioned construction, when a worker positions workpiece cloth to be sewn on the base frame in a stretched state with his/her hands and then operates an operation switch, the air cylinders are driven so that input portions of the clamping mechanism are lowered. The pressing frame is then lowered to the pressing/fixing position such that the clamping mechanism assumes a clamping state and the workpiece cloth is retained in a stretched state.
Furthermore, as a second conventional example, JP-U1-S64-26396 discloses an embroidery frame for use with a sewing machine. The embroidery frame includes a frame (lower frame), an upper pressing frame (upper frame) and an clamping mechanism further including a cloth pressing holder, an actuating arm, a link, a lever, etc.
In the above construction, when the worker operates a knob of the lever so that the lever is lifted up, the upper cloth presser is raised. In this state, when the worker positions the workpiece cloth so that a sewing start position of the cloth corresponds with a mark provided on an upper surface of the upper cloth presser. When the lever is depressed, the upper cloth presser is lowered thereby to clamp the workpiece cloth in cooperation with the frame therebetween.
In the embroidery frame of the first example, however, the clamping mechanism provided on the base frame comprises coupling members, an input lever, a clamp lever and the like which are combined together. Moreover, the air cylinders serve as a drive source for vertically moving the presser frame. As a result, the structure of the clamping mechanism becomes complicated, and the air cylinders necessitate a disposition space. Furthermore, the costs are increased.
On the other hand, the embroidery frame of the second conventional example comprises a four-bar linkage mechanism including the lever which is operated so as to be vertically moved so that the upper cloth presser is swung vertically. Consequently, the vertical dimension of the embroidery frame is increased. Furthermore, since a single lever is operated so that the upper cloth presser is lowered at once to press the entire cloth simultaneously, it is difficult to position the workpiece cloth so that the workpiece cloth is held at a normal position where the workpiece cloth is not inclined relative to the embroidery frame.
The above-described sewing machine capable of performing embroidery sewing is sometimes used to sew a continuous embroidery pattern along an edge of large workpiece cloth such as curtain. When an embroidery pattern is sewn on such large workpiece cloth, embroidery sewing is repeated at a plurality of times while part of the workpiece cloth held by the embroidery frame is changed to another part in sequence. In this case, it is important to position the workpiece cloth accurately so that an embroidery pattern is finely continuous. However, each of the above-described first and second conventional examples has a low accuracy in positioning workpiece cloth, whereupon the embroidery pattern becomes discontinuous.